| 摘要 |
A fan for venting interior air into the environment comprises a motor provided with a shaft, a rotor which is mounted on the shaft, a plurality of fan blades which are fastened rotatably to the rotor, a rotatable round plate which has a plurality of sliding slots and a plurality of communication holes and is mounted on the shaft of the motor, and a fixed round plate which is linked to the rotatable round plate by means of bolts and is likewise mounted on the shaft of the motor. The fan further comprises flyweights which are disposed between the fixed round plate and the rotatable round plate, and one torsion helical spring each, which links the flyweights to the rotatable round plate and resiliently supports the flyweights, so that, during operation of the motor, the flyweights come to engage the rotatable round plate and produce a force acting on the latter in a circumferential direction and produce an angular offset of the round plate. This offset is transferred to the fan blades in order to vent interior air into the environment. If the motor is out of action, the flyweights, under the influence of the torsion helical spring, return to their original position and as a result seal all the air passages between the fan blades.
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